An object of the present invention is to provide an optical communication system and an optical communication method capable of achieving a long transmission distance with a passive element and obtaining redundancy of a ring topology.

The optical communication system according to the present invention is a PON system having a ring configuration, in which an unequal branch optical splitter having a left-right symmetrical configuration is disposed in a trunk fiber wired in a loop shape. An OLT and an ONU have a configuration in which two sets of Tx (transmitter) and Rx (receiver) are mounted. Two sets of Tx (transmitters) and Rx (receivers) in each of a plurality of ONUs are respectively connected to left and right symmetrical ports of one unequally branched light beam SP.

An optical transmission device includes: a first receiver circuit, a second receiver circuit, a switch circuit, a terminator circuit, a packet buffer, a clock generator, and a signal generator. The first receiver circuit converts an optical signal received via a first route into a first electric signal. The second receiver circuit converts an optical signal received via a second route into a second electric signal. The switch circuit selects the first electric signal or the second electric signal. The terminator circuit extracts a packet from an electric signal selected by the switch circuit. The packet buffer stores the packet extracted by the terminator circuit. The clock generator generates a clock signal. The signal generator generates a continuous signal that includes the packet stored in the packet buffer by using the clock signal.

An optical transmission apparatus of an embodiment is an apparatus for redundantly transmitting a multiplexed signal obtained by multiplexing N (N is an integer of 2 or greater) optical signals having different wavelengths, the apparatus including: a first demultiplexing unit to which a first multiplexed signal is input, the first demultiplexing unit configured to demultiplex the input first multiplexed signal into the N optical signals; N first detection units to which the N optical signals demultiplexed by the first demultiplexing unit are respectively input, each of the N first detection units configured to detect presence or absence of deterioration of a corresponding input optical signals of the input optical signals based on a signal level of the corresponding input optical signal; a second demultiplexing unit to which a second multiplexed signal is input, the second demultiplexing unit configured to demultiplex the input second multiplexed signal into the N optical signals; N second detection units to which the N optical signals demultiplexed by the second demultiplexing unit are respectively input, each of the N second detection units configured to detect presence or absence of deterioration of a corresponding input optical signal of the input optical signals based on a signal level of the corresponding input optical signal; and a selection unit configured to select, based on the detection result of presence or absence of deterioration of each of the optical signals by the first detection units and the second detection units, N optical signals having different wavelengths from either the optical signals demultiplexed by the first demultiplexing unit or the optical signals demultiplexed by the second demultiplexing unit.

An alarm processing method and apparatus is disclosed. Specifically, a mechanism of configuring and detecting an LOF pre-alarm is provided. A detection condition of the LOF pre-alarm is that it is detected that a frame alignment failure lasts for first duration. A detection condition of the LOF alarm is that it is detected that a frame alignment failure lasts for second duration. The second duration is less than the first duration. When detecting the LOF pre-alarm, a network device inserts a first maintenance signal frame. The first maintenance signal frame supports frame alignment. In other words, a network device that receives the first maintenance signal frame may perform normal frame alignment, so that no alarm is reported, for example, the LOF alarm is not triggered.

An alarm processing method and apparatus is disclosed. Specifically, a mechanism of configuring and detecting an LOF pre-alarm is provided. A detection condition of the LOF pre-alarm is that it is detected that a frame alignment failure lasts for first duration. A detection condition of the LOF alarm is that it is detected that a frame alignment failure lasts for second duration. The second duration is less than the first duration. When detecting the LOF pre-alarm, a network device inserts a first maintenance signal frame. The first maintenance signal frame supports frame alignment. In other words, a network device that receives the first maintenance signal frame may perform normal frame alignment, so that no alarm is reported, for example, the LOF alarm is not triggered.

A method is presented for supporting SNCP over a packet network connecting to two SDH sub-networks and transporting one or more SDH paths that are SNCP-protected in both SDH sub-networks. The packet network connects to each of two sub-network interconnection points by a working path and a protection path. The packet sub-network may provide the same type of path protection as an SDH sub-network using SNCP, while avoiding bandwidth duplication.

A method is presented for supporting SNCP over a packet network connecting to two SDH sub-networks and transporting one or more SDH paths that are SNCP-protected in both SDH sub-networks. The packet network connects to each of two sub-network interconnection points by a working path and a protection path. The packet sub-network may provide the same type of path protection as an SDH sub-network using SNCP, while avoiding bandwidth duplication.

In an optical communication system, an optical communication device and a plurality of optical transmission devices are loop-connected via transmission line. An optical signal transmission unit of the optical communication device, when no communication interruption occurs in the transmission line, outputs an optical signal addressed to a communication destination device being another optical communication device that communicates with the own device to a transmission line connected to either one of two neighboring optical transmission devices. The optical signal transmission unit outputs, at the time of communication interruption occurring in the transmission line, an optical signal addressed to the communication destination device to both of transmission lines connected to respective two neighboring optical transmission devices. A branch unit of the optical transmission device branches the optical signal input from a neighboring device that is the neighboring optical communication device or another optical transmission device, and outputs branched optical signals to a transmission line connected to a neighboring device different from the neighboring device transmitted the optical signal and a transmission line connected to a subordinate communication destination device of the own device.

Disclosed are an APR protection method and device, and a computer storage medium. A preamplifier PA of each of two optical amplifier units at two ends of a transmission line is connected to a booster amplifier BA of the other amplifier unit by an optical fiber. The method comprises: when a reception state of PA of at least one of two amplifier units is a loss of signal state and a switch chip of said amplifier unit detects a link interruption signal, activating an APR protection state of said amplifier unit which is to turn off BA output of said amplifier unit; when the switch chip of at least one of two amplifier units detects a link conduction signal, deactivating the APR protection state of the present amplifier unit to restore a state of BA of said amplifier unit to a state before the APR protection state is activated.

Disclosed are an APR protection method and device, and a computer storage medium. A preamplifier PA of each of two optical amplifier units at two ends of a transmission line is connected to a booster amplifier BA of the other amplifier unit by an optical fiber. The method comprises: when a reception state of PA of at least one of two amplifier units is a loss of signal state and a switch chip of said amplifier unit detects a link interruption signal, activating an APR protection state of said amplifier unit which is to turn off BA output of said amplifier unit; when the switch chip of at least one of two amplifier units detects a link conduction signal, deactivating the APR protection state of the present amplifier unit to restore a state of BA of said amplifier unit to a state before the APR protection state is activated.